First Characterization of Ostreopsis cf. ovata (Dinophyceae) and Detection of Ovatoxins during a Multispecific and Toxic Ostreopsis Bloom on French Atlantic Coast

Abstract

Blooms of the benthic toxic dinoflagellate genus Ostreopsis have been recorded more frequently during the last two decades, particularly in warm temperate areas such as the Mediterranean Sea. The proliferation of Ostreopsis species may cause deleterious effects on ecosystems and can impact human health through skin contact or aerosol inhalation. In the eastern Atlantic Ocean, the toxic O. cf. ovata has not yet been reported to the north of Portugal, and the only species present further north was O. cf. siamensis, for which the toxic risk is considered low. During summer blooms of unidentified Ostreopsis species on the French Basque coast (Atlantic) in 2020 and 2021, people suffered from irritations and respiratory disorders, and the number of analyzed cases reached 674 in 2021. In order to investigate the causes, sampling was carried out during summer 2021 to (i) taxonomically identify Ostreopsis species present using a molecular approach, (ii) isolate strains from the bloom and culture them, and (iii) characterize the presence of known toxins which may be involved. For the first time, this study reports the presence of both O. cf. siamensis and O. cf. ovata, for which the French Basque coast is a new upper distribution limit. Furthermore, the presence of ovatoxins a, b, c, and d in the environmental sample and in a cultivated strain in culture confirmed the toxic nature of the bloom and allowed identifying O. cf. ovata as the producer. The present data identify a new health risk in the area and highlight the extended distribution of some harmful dinoflagellates, presumably in relation to climate change.

Impacts on Human Health Potentially Caused by Exposure to an Unprecedented Ostreopsis spp Bloom in the Bay of Biscay, French Basque Coast

“…Depending on the substrate, temperature, wind conditions, and water agitation, Ostreopsis spp abundances can increase locally, ranging from a mucilaginous covering on rocks and macroalgae to an extensive brown foam on the water surface. 15 Blooms of Ostreopsis spp are mainly associated with calm waters, higher temperatures, and high nutrient availability. 27 Basque country and North of Spain have rocky coasts and increasing surface (and bottom) water temperatures above 19.5 °C for several months, which is suspected to trigger the blooms.…”

“…12–14 In 2021, a massive HAB, reported by the present authors, occurred in the waters of the French Basque Country. 15…”

Rapid Biotic and Abiotic Transformation of Toxins produced by Ostreopsis. cf. ovata

“…This result raises important questions on the presence of waterborne OVTXs, their transfer to sea spray aerosols and their toxicity to coastal populations. Several outbreaks along the Mediterranean and more recently along the French Atlantic coastlines [80] have been attributed to the aerosolization of OVTX analogs, although these toxins have rarely been detected in sea spray aerosols. The short half-lives of these phycotoxins under biotic and abiotic conditions implies a reduced longevity as waterborne biomolecules, reducing their transfer to the sea spray aerosols.…”

Multiply charged ion profiles in the UHPLC-HRMS analysis of palytoxin analogues from Ostreopsis cf. ovata blooms

“…17,21 The biogeographic expansion of Ostreopsis spp., likely linked to climate change and anthropic pressures on the coasts, is also a matter of study, 22 especially after the important bloom episodes in the Bay of Biscay (France) affecting between 700 and 3000 people in 2021. 23…”

“…17,21 The biogeographic expansion of Ostreopsis spp., likely linked to climate change and anthropic pressures on the coasts, is also a matter of study, 22 especially aer the important bloom episodes in the Bay of Biscay (France) affecting between 700 and 3000 people in 2021. 23 Methodological advances in the last few decades have allowed the efficient and reliable development of extraction and analytical determination methods (chromatography and mass spectrometry) for the most common phycotoxins (saxitoxin, domoic acid, lipophilic toxins, and microcystins) whose presence in seafood and drinking water is strictly controlled by European regulations. 24,25 However, the analogues produced by Ostreopsis have not yet been included in routine monitoring as blooms of these microalgae are still an emerging and poorly characterized issue that requires fundamental research of their dynamics and impacts on human health and the environment.…”